linux-kernel - [ 101/117] proc: Restrict mounting the proc filesystem

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Date:	Tue, 24 Sep 2013 17:19:27 -0700
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org, Andy Lutomirski <luto@...capital.net>,
	"Eric W. Biederman" <ebiederm@...ssion.com>
Subject: [ 101/117] proc: Restrict mounting the proc filesystem

3.11-stable review patch.  If anyone has any objections, please let me know.

------------------

From: "Eric W. Biederman" <ebiederm@...ssion.com>

commit aee1c13dd0f6c2fc56e0e492b349ee8ac655880f upstream.

Don't allow mounting the proc filesystem unless the caller has
CAP_SYS_ADMIN rights over the pid namespace.  The principle here is if
you create or have capabilities over it you can mount it, otherwise
you get to live with what other people have mounted.

Andy pointed out that this is needed to prevent users in a user
namespace from remounting proc and specifying different hidepid and gid
options on already existing proc mounts.

Reported-by: Andy Lutomirski <luto@...capital.net>
Signed-off-by: "Eric W. Biederman" <ebiederm@...ssion.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 fs/proc/root.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/fs/proc/root.c
+++ b/fs/proc/root.c
@@ -110,7 +110,8 @@ static struct dentry *proc_mount(struct
 		ns = task_active_pid_ns(current);
 		options = data;

-		if (!current_user_ns()->may_mount_proc)
+		if (!current_user_ns()->may_mount_proc ||
+		    !ns_capable(ns->user_ns, CAP_SYS_ADMIN))
 			return ERR_PTR(-EPERM);
 	}

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